[Mathew Reuther]

Be as exacting as you'd like. I am not bothered at all. I was not aware that there was a (format) argument which could even be included. Is that something you typically use? I've never seen it laid out like that. Do you recommend using that format declaration as a standard in your css? (and what is the format declaration then for truetype? "truetype"?

As for the mainifest, here is an example of what they look like. This is, mind you, auto-generated by Sigil...I do not hand code it:

(inside the manifest section of the content.opf file)

<item href="Fonts/display-font.ttf" id="display-font.ttf" media-type="application/x-font-ttf" />

<item href="Fonts/header-font.otf" id="header-font.otf" media-type="application/vnd.ms-opentype" />

Now, as a test, if you could just tell me the name of a font or two that you know will work that come from a source that is free (fontsquirrel, dafont, google fonts, etc.) I can try to use those and see what happens. That way we know that the fonts themselves DO work in another file.